Range control system



Dec. 3, .1935. H. M. BIE-BEL 2,023,114 v RANGE CONTROL SYSTEM File@ March 50, 19:54

Patented Dec. 3, 1935 UNITED STATES PATENT OFFICE RANGE CONTROL SYSTEM Herman M. Biebel, Oakmont, Pa., signor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 30, 1934, Serial No. 718,273 12 Claims. (Cl. 219-20 quickly installable apparatus for selectively ob`I taining any one of a` number of different timetemperature cycles in a cooking chamber.

Another object of my invention is to provide av thermo-electric control system for a cooking chamber that shall comprise a minimum number of component parts or elements.

Other objects of my invention will either rbe apparent from the following description of the 15 elements entering into my invention and of their 1 operation, or will be more specifically pointed out hereinafter.

v In practicing my invention, I provide, in combination or in cooperation with, a cooking chamber having a heating element therein, which is controlled to obtain any one of a plurality of different time-temperature cycles through the agency of a single-cycle thermally-actuable lswitch assembly and a plural-,cycle vthermallyactuable switch assembly, which severally control Y the energization of the heating element. For this purpose, the two switches are 'electrically connected in parallel, and the single-cycle switch ,is provided with latching means to hold it in its 30,0pen position after its first actuation to suc position. I

Reference is here made to applicants copending applications relating to similar subject matter, Serial Numbers 718,272, 718,274,- 718,275, 718,276, 718,277; led concurrently herewith and also to an application by F. S. Wheeler, Serial No.

Two time-temperature cycles used `with or in the cooking chambers of electric ranges, such as 40 the oven, are already well known. One of these is that in which an electric heating element is energized'at a certain time'by time-controlled or manually-controlled means, the temperature in the cooking chamber being raised until a thermal device lcated therein reachesa predetermined the necessary cooking ofthe roast is eiected byv stored heat. Another method widely used is/,that in which a the heating element.

thermal element is operatively associated with the cooking chamber of lan electric range, and controls a suitable circuit controller for the heating element, whereby the heating element is intermittently sequentially energized and deener- 5 gized to maintain a certain average temperature in the cooking chamber.

My invention has more particularly 4to do with a temperature cycle in the cooking chamber which combinesboth of these older cycles in that 10 the temperature isvraised, by the heating element,

. to a momentary peak temperature, whereupon theV heating element is deenergized, after which, when the chamber temperature has dropped to` a lower value, say, 300 F., it is maintained at sub- 15 stantially that value for the rest of the time necessary to properly cook the roast.

It is obvious that the use of a thermal control element located in the oven chamber and follown ing the temperature variations, either of the 20 chamber or ofthe material being cooked, is a very eiective devicel to be used in the control of This isV for the reason particularly, that, as the amount of energy translated lnto heat in the heating element is usually 25 fixed, the length of time necessary to sear a roast will depend upon the weight of the roast itself, that is, the larger the roast, the longer will it require to have the chamber temperature or the temperature of the thermal element reach a value 30 of 500 F., at which temperature the heating element is temporarily deenergized, such deenergization continuing until the lower predetermined sustained. or maintained temperature is reached.

' In the accompanying single sheet of drawings: 35

Figure 1 is a view, mainly schematic, of a temperature control system embodying my invention; Fig. 2 is a fragmentary view of the mechanism shown in front elevation in Fig. 1, as seen in lateral section; and 40 Fig. 3 is a schematic diagram of connections of amodiiled system embodying my invention.

Referring iirst to Figs. 1 and 2 of the drawing,

` I have there illustrated an oven casing Il enclosing a cooking chamber i3 having an electric 45 heating element i5 located therein to heat the same. I have shown the oven and the heating elements schematically only,.as the design and construction thereof form no part of my present invention. 50

A supply circuit for energizing the heating element I5 is constituted by supply-circuit conductors LI and L2. As it may be desirable to utilize a time-controlled means to start and to stop the operation of the oven, I have shown a clock I1 55 vto which controls contact members I9 operatively associated therewith to close'and open the circuit as desired by an operator, this being accomplished in a. manner now well known in the art.

I provide a pair of parallel-connected circuitcontrolling instrumentalities in the form of thermany-actuable switch assemblies,. one of these being indicated by the numeral 2| and the other being indicated by the numeral 23. The device 2| may be designated as a single-cycle circuit controller or switch, while device 23 is a plural-cycle switch or circuit controller. The 'signiiicance of these titles will be more fully brought out hereinafter.

The device 2| includes a mercury switch 25 actuated by a. bimetal strip 21, which strip may be of spiral shape substantially as shown in the drawing. One end of the spiral bimetal member 21 is fixed as against a rear plate 29, by a pin 3|,

while the other end of the spiral is operatively secured to the mercury tube switch 25, al1 in a manner now well known in the art. The normal or closed position of switch 2| is that shown in the drawing where the tube is substantially horizontal, and it is to be understood that upon an increase of the temperature of the bimetal spiral 21, it will move in such manner as to turn the sition after its first actuation thereto. A spring.

4I cooperates with arm 31 to pull itagainst a stop 43 whereby to reduce the friction between the cooperating inclined surfaces of the lower end of latch 31 and of lug 35. 'I'he latch thus prevents reclosing of the circuit of the switch 2| by the action of the thermally-actuable member thereof after' having been moved into open position thereby. 'Y

The second circuit-controlling instrumentality 23 includes a mercury tube switch 45 and a bimetal spiral 41 arranged and operating in substantially the same manner as the corresponding parts 25 and 21 of device 2|.

Means for adjusting the respective switches 2| and 23, whereby to vary the temperatures at cuit, may comprise a hand lever 49 (see Fig. 2)

or any other suitable or appropriate means for` obtaining the saine results, namely, the adjustment of the thermally-actuable circuit controllers to vary their operating temperatures. It is to be particularly noted that such thermally-actuable switches may be purchased in the open market, and it is for this reason that I have elected not to show all of the details of these devices, but rather to show only suflcient structure to indicate the general construction and to describe the desired operating characteristics of these several circuit controlling instrumentalities.

As shown schematically in the drawing, the two devices 2| and 23 may be located in a suitable metal casing 5|, which may be secured in proper position within the oven chamber I3, as by machine screws 53, the shaft 39 then extending forwardly .of the oven structure II, and being provided with a knob 55.

Means for rendering the respective switches 2| and 23 effective and ineffective are provided in duplicate. One means includes a manually operable switch arm 51 operatively associated with device 2| and a manually operable switch arm Means to energize and deenergize the circuit 10 4 of the heating element I5, irrespective of the clock I1, may be provided in the form of a manually actuable switch which is here shown as two switch arms 1I and 13, although, of course, I may use any other form of circuit-controlling means, such 15 as a snap switch.

I wish to point out here that the devices 2| and 23 just described are vGormected in parallel circuit relation with 'one another, so that they severally control the' circuit of the heating element in a 20 manner to be hereinafter set forth. In other words, each mercury switch controls directly the circuit of the heating element without the use of any v intermediate circuit-controlling devices. Where the heating element is of relatively large 25 capacity; 4that is, where it is desired tocarry 20 to 40 amperes at I||l volts, the mercury switches must, of course, each be of corresponding current-carrying capacity.

It may be desirable, therefore, to arrange for 30 the use of smaller mercury switches, and a system whereby this can be elected is shown in- Fig.

3 of the drawing. The supply circuit is again indicated by conductors LI and L2, the heating element being indicated as before by numeral 35 I5. The.circuit of heating element I5 is controlled by a'contactor 8|, including a coil 83, a movable armature core 85, a contact bridging member 81, and two spaced cooperating contact `members 89 connected in circuit with heating 40 element I5. A contactor of this kind is well known in the art, and can bemade at a relatively small cost.

Means for controlling the energization of actuating coil 83 of contactor 8| includes a single- 45 cycle thermally-actuable switch assembly 9| and a plural-cycle thermally-actuable switch assembly 93, these being substantially the same as was hereinbefore described in connectionwith Fig. 1 I of the drawing, where similar devices are num- 50 bered 2| and 23, respectively. In view of the similarity of devices 9| and 93 to devices 2| and 23, it is believed unnecessary to further describe these switches in detail, except to state that the current-carrying capacity of these mercury 55 switchesmay now be measured in terms of one ampere or less, this being the amount of current usually required for an actuating coil of a contactor.

Means for rendering the respective switches 9| 60 and 93 effective and ineffective at the will of an .mercury switches of higher current-carrying capacity. 10

I wish to point out here that while I have illustrated and, described mercury switches actuated by a bimet'al element, I do not wish to be limited thereto, and it is obvious that any form of thermally-actuable circuit controlling means may be 75 utilized, so long as one of the circuit-controlling devices is 'a single-cycle switch, which is latched open after its first movement to open position, while the second switch is a plural-cycle switch operative continuously until deenergization of the entire system is effected.

As has already been set forth, one of the timetemperature cycles which it is desired to obtain with the two instrumentalities hereinbefore described includes a substantially momentary peak temperature on the order of 500 F. or over fol- -lowed by a sustained or maintained lower temperature on the order of 300 F. or so. Device 2| or device 9|, as the case may be, is adjusted so that it will operate to open its circuit at about 500 F. while device 23, or device 93, is adusted to operate to open its circuit at about 300 F.

Assuming that the above-mentioned adjustments have been made, and that it is desired to obtain the momentary peak and the lower maintained temperature cycle, switches -51 and 59 of Fig. 1 are both closed manually, and if the main circuit-energizing switch (members 1I and 13) is also closed, the heating element I5 will be energized, assuming, of course, that the contacts I9 have been closed either manually or by the clock I1, so that the chamber temperature will increase.` At a temperature of 300 F. switch 23 is moved to open position, but since switch 2| is still in its closed position, energization of the heating element I5 continues without any change. However, at a temperature of 500 F., switch 2| is moved to open position and is then held in such position by reason of the latch 31. The heating element I 5 is then deenergized, and the temperature in the cooking chamber gradually decreases from the momentary peak temperature of 500 F. When the chamber temperature reaches a value of about 300 F., switch 23 is moved to its closed position so that the heating element I5 is re-energized, thereby causing an increasein the chamber temperature. At a certain slightly higher temperature in the cooking chamber, switch 23 is again moved to open position, and it is, of course, understood that there vmay be a small temperature differential between the open and the closed positions of switch 23, this temperature differential depending entirely upon the design of the switch. In other words, an average temperature of approximately 300 F. will be maintained in the cooking chamber as long as the energizing circuit is otherwise closed.

Let it be assumed that we desire to obtain a peak temperature cycle only, the operator can then use either switch 53 associated with device 23 or the mechanical moving means 63 associated with device 23 to render switch 23- ineiective. If switch 59 is opened, the circuit through mercury .switch 45 is, of course, interrupted, and if arm 53 is turned so as to turn switch 45 on its pivot and into open position, the same'result is obtained. The heating element I5 is now controlled solely by the device 2|, which interrupts the circuitv through the heating element at about 500F. and is then latched in its open position, whereafter the cooking chamber cools gradually by radiation of heat therefrom.

Letit be assumed that it is desired to operate the oven at a substantially constant but lower maintained temperature, the operator may open switch 51 or turn arm. 6I to render device 2| ineffective. Energization of the heating element I5 is now controlled solely by switch 23, which intermittently sequentially energizes and deenergizes the heating element I5 to maintain a substantially constant average temperature of, say, 300 F. in the oven chamber.

Substantially the same comments hold in regard to the system shown in Fig. 3 of the drawing, where the respective thermally-actuable 5 switches 9| and 93 severally control the circuit of contactor coil 33, which in turn, through its contact members and contact bridging member, controls the circuit of heating element I 5.

The device and system my invention l0 thus provides very simple, relatively inexpensive, n and easily installed circuit-controlling instrumentalitl for so controlling the energization of the heatinglelement, at the will of an operator, as tol permit of. obtaining any one of a number 15 of different temperature cycles dn a cooking chamber. The respective circuit controlling switches are easily obtained in the open market or modiiled.

Various further modications may be made in 20 the device embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or are set forth in the appended claims.

, I claim as my invention:

1. In an electric cooking appliance including a cooking chamber and an electric heater therefor, a unitary thermally-actuable circuit controller for the heater responsive to chamber temper- Aature and operable to open position at a certain temperature, a second unitary thermally-actuable circuit controller responsive to chamber temperature and operable to open position at a higher temperature than the first-named circuit controller, said second controller being electrically connected in parallel to the first-named controller thereby to automatically continue energization of the heating element to prow'de a lower temperature in said chamber after movement of 40 said second controller to open position, and means operatively associated with the second circuit controller to hold it in said open position onceit has been moved thereinto.

2. In an electric cooking appliance including a cooking chamber and an electric heating element therefor, a thermally-actuable switch movable in lresponse to variations in chamber temperature connected in the circuit of the heating element and operable to open position at a certain temperature,I a second thermally-actuable switch movable in response to variations in chamber said second switch being electrically connected in parallel with the iirst switch thereby to automatically continue energization of the heating element to provide a lower temperature in said chamber after movement of the first switch to open position, and. manually-operable latching means associated with the first swin to hold it in open position after having been moved into such position.

3. In an electric cooking appliance including a cooking chamber and a heating element therefor, a pair of unitary thermally-actuable switches severally controlling the energization of the heatlng element, said switches being operable in response' to variations inchamber temperature and one of said switches being operable at a higher temperature than the other, electric connections between the two switches whereby the initial control of the heating element is effected by the switch operable at the higher temperature, and

means operatively associated with the switch operable at higher temperature to render it ineffective after its first operation to open position and to transfer the control of the heating element to the switch operable at lower temperature. 4. In an electric cooking appliance including a,V cooking chamber and a heatingelement there--` fon control means for the heating element to obtain a peak temperature and then a maintained temperature cycle in the cooking chamber, said means comprising a ilrst thermally-actuable switch for the heating element, movable in response to variations in chamber temperature and operable at a certain temperature, a second thermally-actuable switch for the heating' element movable in response'to variations in the chamber temperature and operable at a higher temperature than the irst switch, electric connections between the two switches to cause the second switch to control the heating element until a peak chamber temperature has been reached, and means to render the second switch ineiective after its iirst operation to open position, the rst switch thereaftersequentially energizing and deenergizing the heating element to maintain a lower temperature in the cooking chamber.

5. In an electric cooking appliance including a cooking chamber and a heating element therefore, means for obtaining any one ofthree temperature cycles in the cooking chamber, said means comprising a first thermally-actuable switch responsive to chamber temperature controlling the energization of the heating element and operable at a certain temperature, a second`A element, wherebyupon rendering effective the second switch a peak temperature cycle is obtained, upon rendering effective the first switch only a maintained lower temperature cycle is obtained and whereby upon rendering both switches .effective a combined initial peak temperature and a subsequent maintained lower temperature cycle is obtained in a cooking chamber.

6. A device as set forth in claim 4, in which the means rendering the second switch ineffective is a latch cooperating with the switch to hold it i'n open position.

'7. A device as set forth in claim 4, in-which the means rendering. the second switch ineffective is a manually operable latch cooperating with the switch to hold it in openv position after its first operation to such position.

8. In an electriccooking appliance including a cooking chamber and a heating element therefor, a unitary single-cycle thermally-actuable switch assembly for controlling the energization of the heating element and operable at a peak temperature in the cooking chamber, a unitary pluralcycle thermally-actuable switch assembly for controlling thefenergization of the heating element and operable at a lower temperature in the cooking chamber, and electric conductors connecting said switches in parallel with each other and in circuit with the heating element, whereby the single-cycle switch controls the energization of the heating element until a peak temperature is reached in` the cooking chamber when the heat- Y 'heating element to obtain a peak temperature and then a maintained lower temperature in the cooking chamber, said means comprising a single- 10 cycle peak temperature thermally-actuable unitary switch assembly responsive to chamber temperature and a plural-cycle maintained. lower temperature thermally actuable unitary switch assembly responsive to chamber temperature, 15 conductors connecting said switches in parallel with each other and to lcontrol the heating element, said single-cycle peak temperature switch controlling the energization of the heating element until a peak temperature in the cooking 20 chamber is reached then moving to and remaining in open position whereafter the maintained lower temperature switch intermittently sequentially energizes and deenergizes the heating element to maintain aA lower temperature in the 25 heating chamber. l

10. A device as set forth in claim 4, in which the means rendering the respective switches ineiective are manually-actuable means for moving the switches to open position. 30 11.'In an electric cooking appliance including a cooking chamber and a heating element therefor, a 'thermally-actuable unitary switch assembly responsive to chamber temperature controlling the energization of the heating element and 35 operable at a peak chamber temperature, a second thermally-actuable unitary switch assembly responsive to chamber temperature controlling the energization of the heating element and operable at a lower maintained chamber temperature, con-V 40 ductors connecting the two switches in parallel with each other, a manually-releasable latch for the peak temperature switch to hold it in'open position after it has moved into such position, and means operatively associated with the re-'45 spective switches to render them effective and ineiTective at the will of an operatonwhereby upon rendering both switches effective a momentary peak temperature in the chamber and then a lower maintained temperature therein is obtained, and upon rendering eiective the maintained temperature switch assembly only a substantially constant lower maintainedtemperaturc in the chamber is obtained. 55 l2. In an electric cooking appliance including a cooking chamber and a heating felement therefor, means for controlling the heating element to obtain a peaktemperature and then a maintained lower temperature inthe cooking chamber, 60

said means comprising a lirst thermally-actuable unitary switch for the heating element, movable in response to variations in chamber temperature and operable at substantiallyl the desired maintained temperature value, a second thermallyactuable unitary switch for the heating-element, movable in response to variations in chamber temperature and operable at a desired peak temperature, electric conductors connecting, the two 0 switches in parallel with each other and means associated with the second switch to prevent reclosing thereof after its first operation to open position.

HERMAN M. BIEBEL. 

